Tim Duncan takes a jumper over Ryan Anderson as the Spurs play the Pelicans at the AT&T Center on December 31, 2014.

Tim Duncan takes a jumper over Ryan Anderson as the Spurs play the Pelicans at the AT&T Center on December 31, 2014.

Photo: San Antonio Express-News

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Tim Duncan of the Spurs (center) fights for an offensive rebound with Houston's Josh Smith (left) as Dwight Howard looks on during the first half of their game at the AT&T Center on Sunday, Dec. 28, 2014. The Spurs beat the Rockets 110-106. MARVIN PFEIFFER/ mpfeiffer@express-news.net less

Tim Duncan of the Spurs (center) fights for an offensive rebound with Houston's Josh Smith (left) as Dwight Howard looks on during the first half of their game at the AT&T Center on Sunday, Dec. 28, 2014. The ... more

Photo: San Antonio Express-News

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San Antonio Spurs' Tim Duncan looks for room around Oklahoma City Thunder's Russell Westbrook during first half action Thursday Dec. 25, 2014 at the AT&T Center.

San Antonio Spurs' Tim Duncan looks for room around Oklahoma City Thunder's Russell Westbrook during first half action Thursday Dec. 25, 2014 at the AT&T Center.

Photo: San Antonio Express-News

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San Antonio Spurs forward Tim Duncan reaches over to try and block Memphis Grizzlies guard Courtney Lee during the second half at the AT&T Center, Wednesday, Dec. 17, 2014. The Grizzlies won 117-116 in triple overtime. less

San Antonio Spurs forward Tim Duncan reaches over to try and block Memphis Grizzlies guard Courtney Lee during the second half at the AT&T Center, Wednesday, Dec. 17, 2014. The Grizzlies won 117-116 in triple ... more

Photo: San Antonio Express-News

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Tim Duncan gets up for a shot between Jordan Hill (left) and Jeremy Lin at the Spurs game against the Lakers at the AT&T Center on December 12, 2014. Duncan was called for an offensive foul, clipping Lin on the chin going up. less

Tim Duncan gets up for a shot between Jordan Hill (left) and Jeremy Lin at the Spurs game against the Lakers at the AT&T Center on December 12, 2014. Duncan was called for an offensive foul, clipping Lin on ... more

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San Antonio Spurs' Tim Duncan looks for room around Minnesota Timberwolves' Gorgui Dieng during second half action Saturday Dec. 6, 2014 at the AT&T Center. The Spurs won 123-101.

San Antonio Spurs' Tim Duncan looks for room around Minnesota Timberwolves' Gorgui Dieng during second half action Saturday Dec. 6, 2014 at the AT&T Center. The Spurs won 123-101.

Mavericks Tyson Chandler and Dirk Nowitzki swarm Tim Duncan under the backboard on a shot in the first half as the Spurs open the season against the Dallas Mavericks at the AT&T Center on October 28, 2014.

Mavericks Tyson Chandler and Dirk Nowitzki swarm Tim Duncan under the backboard on a shot in the first half as the Spurs open the season against the Dallas Mavericks at the AT&T Center on October 28, 2014.

High School

Duncan was second team to Kawhi Leonard’s first team. And while Leonard was also named the Defensive Player of the Year earlier this spring, the rare award that Duncan has never won, Leonard faces a timeline he likely has trouble even imagining.

Duncan has now made 15 All-Defensive teams, and the next highest total by anyone in league history is 12. If Leonard continues to be on such a team every season, he will tie Duncan in 2028.

Duncan’s latest honor fits with his season. Based on 36-minute averages, Duncan’s blocks and rebounds were about the same as in his prime. His series against the Clippers further extended that, with a 27-11 Game 7 that featured two, must-make free throws.

And when he missed blocking Chris Paul by the space that is between Letterman’s front teeth? There was nothing about the performance that suggests Duncan should retire.

Still, people bow out while they can still perform, and Letterman did a year ago. Then, he phoned his boss at CBS and said, “It’s been great, you’ve been great, and the network has been great. But I’m retiring.”

Duncan could say the same. Right now, the Spurs don’t know.

Or maybe June 24, 2014 offers some insight. Then, Letterman came back from a commercial break to greet Duncan.

“I don’t know how old you are,” Letterman said, “but you and I are about the same age.”

Duncan hears this kind of humor all the time from teammates. So he was ready when Letterman, 67 at the time, lumped the two of them together.

“Basically,” Duncan said, laughing.

Letterman went on. He talked about Duncan’s fifth title, and what it must have meant to him, and he wanted to know if Duncan had thought about walking away while on top.

“I did,” Duncan admitted, and everyone in San Antonio should understand what this means.

If he thought about retiring last year, how serious must he be today?

Duncan continued, and what he said then applies now: “I thought about calling it a year, calling it a career. But I felt I could do at least one more year. I felt I was still effective. I thought I could still play and help the team.”

There are other factors. Health and family are two, and Duncan shot down a third when Letterman asked him about the grind of travel.

“We’re taken care of,” Duncan said, smiling, and Letterman followed with a classic line.

Duncan adheres to the theory, Letterman said, that there’s “no whining on the yacht.”

Duncan understands his life on an NBA yacht hasn’t been a bad one. So if he’s basing his decision on whether he could still be effective, whether he “could still play and help the team,” then why wouldn’t he come back again?

Wednesday’s award only confirms what his season already did.

No matter what Duncan decides, he will always be the final NBA champion to be honored by Letterman. And that night last June, after Letterman pulled an NBA trophy from behind his desk, and after Paul Shaffer led a jazzy rendition of “We Are the Champions,” Duncan and Letterman stood and waved to the audience.